Impact of surface characteristics to microlayer, bubble dimensions and departure in nucleate boiling

In this work, an experimental and theoretical investigation about the impact of surface characteristics (wettability and roughness) on the microlayer is reported. Stainless steel heaters with five different surface characteristics were employed in the experiment. Laser polishing, wet-etching, and self-assembled monolayer (SAM) coating were applied to control the roughness and wettability of the heater surface. The experiments were carried out in a vertical boiling process with deionized water at atmospheric pressure. Based on these experimental results, the impact of surface characteristics to the effective microlayer thickness was quantitatively analyzed and formulated. Moreover, after the bubble is complete evaporated, the dry spot underneath bubble determines the surface tension of the bubble, which is also investigated in this work. The surface tension impacts the bubble motions and departure. Consequently, in the paper, the impact of surface characteristics on the microlayer, bubble dynamics and the impact mechanisms is quantitatively analyzed. The understanding and findings from this work will be helpful to improve the modelling of bubble dynamics.